Commit d7d82944 authored Jan 05, 2011 by Mike Galbraith Committed by Ingo Molnar Jan 18, 2011

sched: Fix signed unsigned comparison in check_preempt_tick()



Signed unsigned comparison may lead to superfluous resched if leftmost
is right of the current task, wasting a few cycles, and inadvertently
_lengthening_ the current task's slice.

Reported-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1294202477.9384.5.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent fce20979

kernel/sched_fair.c

+3 −0

Original line number	Original line	Diff line number	Diff line
	@@ -1062,6 +1062,9 @@ check_preempt_tick(struct cfs_rq cfs_rq, struct sched_entity curr)
	struct sched_entity *se = __pick_next_entity(cfs_rq);		struct sched_entity *se = __pick_next_entity(cfs_rq);
	s64 delta = curr->vruntime - se->vruntime;		s64 delta = curr->vruntime - se->vruntime;

			if (delta < 0)
			return;

	if (delta > ideal_runtime)		if (delta > ideal_runtime)
	resched_task(rq_of(cfs_rq)->curr);		resched_task(rq_of(cfs_rq)->curr);
	}		}